Bacteria Characteristics of Bacteria | Reproduction of Bacteria

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Bacteria

Characteristics of Bacteria | Reproduction of BacteriaBacteria Characteristics of Bacteria | Reproduction of Bacteria1Single-celled prokaryotic organisms

Contain cell walls composed of a protein and carbohydrate matrix called peptidoglycanStructurally different from Archaea or plants

Do not contain a nucleus or membrane-bound organelles

Characteristics of BacteriaThere are thousands of different types of bacteria, but all are single-celled prokaryotic organisms. Many form clusters or colonies of cells.

Most bacteria are smaller than 10 micrometers (m), and some are as small as .1 m. To put this into perspective, a grain of fine beach sand is 90 m in diameter, and the thickness of human hair ranges from 50-70 m.

All bacteria contain cell walls composed of a protein and carbohydrate matrix called peptidoglycan.

These cell walls are structurally different when compared to cell walls in Archaea or plants.

Since bacteria are prokaryotes, they do not contain a nucleus or membrane-bound organelles. 2Nucleoid region within bacteria where DNA is organized Plasmids are small circular segments of bacterial DNAAll contain: Plasma membraneCytoplasmRibosomes Capsule a protective coating outside of bacterial cell wallsSome contain:Flagella which are used for locomotionPili function in some forms of reproduction

Characteristics of BacteriaDNA is instead organized into a nucleoid region and small segments of plasmids.

Bacteria also contain a plasma membrane, cytoplasm, ribosomes and a protective coating known as a capsule.

Some bacteria also contain flagella that are used for locomotion and pili (singular pilus) that function in some forms of reproduction.

3Characteristics of Bacteria

Bacteria can contain structures such as a nucleoid region, plasmids, cell wall, and flagellum. 45

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Streptococcus Causes Strep Throat67Bacillus - E. coli

78Spirochetes

8Bacteria are very diverseSome are autotrophsSome perform photosynthesis with chlorophyllSome perform chemosynthesisDeep sea vents, other ocean environments, and hot springsSome are heterotrophicObtain energy by absorbing or ingesting foodCharacteristics of Bacteria

Ecologically, bacteria are very diverse.

Some bacteria are autotrophic, meaning that they can produce their own food.

Of these bacteria, some perform photosynthesis with chlorophyll, while others perform chemosynthesis.

Chemosynthetic bacteria have been discovered in deep sea hydrothermal vent ecosystems, other ocean environments, and terrestrial environments such as hot springs.

Other types of bacteria are heterotrophic and must obtain their energy by absorbing or ingesting their food source.

9Aerobic bacteria require oxygen in the process of cellular respiration

Anaerobic bacteria do not use oxygenCharacteristics of BacteriaLike all living things, bacteria respire. Aerobic bacteria require oxygen in the process of cellular respiration to release energy from food.

Anaerobic bacteria, in contrast, do not use oxygen.

Of these, obligate anaerobes cannot grow in the presence of oxygen.

Some are even killed in oxygen-rich environments.

Facultative anaerobes are more flexible. They may prefer oxygen, but are able to use fermentation pathways if oxygen is not available.

10Cell division = reproduction in prokaryotes

Binary fission simplified form of cell division used by bacteria

Steps:DNA is replicated Cell increases in size, splits in two Plasma membrane pinches together and a new cell plate forms Control of the bacterial cell cycle: growth rates, biochemical signals, and environmental conditionsReproduction of BacteriaIn single celled organisms, cell division is the equivalent of reproduction.

Bacteria typically use a simplified form of cell division known as binary fission.

In binary fission, once the DNA is replicated, the cell increases in size and splits in two cell.

As in plant cells during cytokinesis, the plasma membrane pinches together and a new cell plate forms between the daughter cells.

The cell cycle in bacteria is controlled by growth rates, biochemical signals, and environmental conditions.

11Reproduction in Bacteria

Binary fission in bacteria is a simplified form of cell division.

12Ability to exchange DNA with another bacterium

Conjugation exchange of DNA in bacteriaSimilar to genetic recombination in eukaryotesReproduction in BacteriaMany bacteria also have the ability to exchange DNA with another bacterium.

Similar to genetic recombination in eukaryotes, this exchange of DNA is termed conjugation.

13Donor bacterium connects to another bacterium using pilus DNA is transferred to the recipient cell through pilusAided by proteinsDNA donated can be a plasmid Donated DNA may contain beneficial genesReproduction in Bacteria

In conjugation, a donor bacterium connects to another bacterium with a pilus, an extension of the plasma membrane.

Once the two cells are in direct contact and aided by proteins, the DNA is transferred to the recipient cell through the tunnel-like opening created by the pilus.

Often the DNA donated is a plasmid and contains genes that are beneficial to the bacterium. For example, plasmids may contain genes for resistance to antibiotics or enhanced metabolic properties.

14Some bacteria disrupt the health of other organisms

Pathogenic bacteria that cause disease

Bacterial diseases are spread through: Droplets in the airDirect contact with the bacterium On surfacesIn fluidsThrough contaminated foodDiseases Caused by BacteriaSome bacteria can disrupt the health of other organisms.

Bacteria that cause disease are termed pathogenic.

Each disease is different, but generally bacterial diseases are spread through droplets in the air (airborne), direct contact with the bacterium on surfaces and in fluids, or contaminated food.

15Streptococcal disease any bacterial disease, including strep throat, that is caused by streptococcus genusCommon infection in childrenHighly contagiousSymptoms: Sudden feverAchesNauseaRed throat with possible white patchesTreated with antibiotics

Diseases Caused by Bacteria

Several species of Streptococcusbacteria can cause a number of diseases, most commonly streptococcal pharyngitis, known as strep throat.

While not every sore throat is caused by bacteria, this infection is common, especially in children.

Highly contagious, the infection is spread by contact with nasal or throat secretions.

Other symptoms include sudden fever, aches, nausea, and red throat with possible white patches.

It is important that strep throat is treated with antibiotics to avoid infections in the ears, tonsils, or sinuses.

16Impact of bacteria on biosphereProduce oxygenBacteria decompose dead plant and animal matterRelease carbon dioxide into atmosphere

Multicellular organisms have bacteria living in their digestive tractMutualistic relationshipBacteria break down indigestible compounds for host to absorbBacteria receive nutrition and a place to live

Ecological Impact of Bacteria

Bacteria impact the biosphere in a number of ways.

Ocean-dwelling cyanobacteria produce a portion of the oxygen we breathe every day.

In food webs, bacteria play an important role as decomposers, breaking down dead plant and animal matter.

They return nutrients to the soil and release carbon dioxide into the atmosphere as part of the carbon cycle.

Bacteria can also maintain the health of other organisms. Many multicellular organisms (including humans) have bacteria living in their digestive tract, forming a mutualistic relationship.

The bacteria break down indigestible compounds for the host to absorb.

In return, the bacteria receive nutrition and a habitat, or a place to live.17Bacteria maintain health of organisms through biotechnology

Vaccines and antibiotics Bacteria used in genetic engineeringEcological Impact of Bacteria

Bacteria also indirectly help maintain the health of organisms through biotechnology.

Humans use bacteria to develop vaccines and antibiotics.

For example, Streptomyces griseus produces a substance toxic to competing bacteria. Biotechnologists purify this substance to produce the antibiotic streptomycin.

Lactobacillus bulgaricus is one type of bacteria used to produce dairy products such as yogurt and certain kinds of cheese.

Bacteria are also used to perform genetic engineering. These technological advances resulting from the study of bacteria help keep humans healthier.

18Bacteria help in producing and cycling nitrogenBacteria in soil make nitrogen useable through nitrogen fixationBreak down dead organisms and waste into ammoniumOther bacteria then change ammonium into nitrates for plants

These bacterial processes allow nitrogen to cycleFrom atmosphereThrough food chainWithin soilEcological Impact of Bacteria

Bacteria also help in producing and cycling nitrogen, an element essential for life.

Bacteria in the soil can make nitrogen useable through nitrogen fixation, ammonification, and nitrification.

Bacteria also break down dead organisms and waste into ammonium.

Other bacteria then change this ammonium into nitrates for plants to use.

These bacterial processes allow nitrogen to cycle from the atmosphere, through the food chain, and within the soil.

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Nitrogen Cycle

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